Selection of Ionic Liquids to be Used as Separation Agents for

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Selection of Ionic Liquids to be used as Separation Agents for Terpenes and Terpenoids Mónia Martins, Urszula Maria Domanska, bernd schroder, Joao A.P. Coutinho, and Simao P. Pinho ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.5b01357 • Publication Date (Web): 08 Dec 2015 Downloaded from http://pubs.acs.org on December 15, 2015

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ACS Sustainable Chemistry & Engineering

Selection of Ionic Liquids to be used as Separation Agents for Terpenes and Terpenoids Mónia A. R. Martins1,2, Urszula Domańska2, Bernd Schröder1, João A. P. Coutinho1 and Simão P. Pinho3*

1 2 3

Departamento de Química, CICECO, Universidade de Aveiro, 3810-193 Aveiro, Portugal. Physical Chemistry Department, Warsaw University of Technology, 00-661 Warsaw, Poland. Associate Laboratory LSRE/LCM, Departamento de Tecnologia Química e Biológica, Instituto

Politécnico de Bragança, 5301-857 Bragança, Portugal.

*Corresponding author: Phone: +351 273303086; Fax: +351 273313051; E-mail: [email protected]. 1 ACS Paragon Plus Environment


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ABSTRACT In this work ionic liquids are evaluated for the first time as solvents for extraction and entrainers in separation processes involving terpenes and terpenoids. For that purpose activity coefficients at infinite dilution, γ 13∞ , of terpenes and terpenoids, in the ionic liquids [C4mim]Cl, [C4mim][CH3SO3], [C4mim][(CH3)2PO4], and [C4mim][CF3SO3] were determined by gas-liquid chromatography at six temperatures in the range (398.15 to 448.15) K. Based on the experimental values, a correlation of γ 13∞ with an increase of the solubility parameters is proposed. The infinite dilution thermodynamic functions were calculated showing the entropic effect is dominant over the enthalpic. Gas-liquid partition coefficients give indications about the recovery and purification of terpenes and terpenoids from ionic liquid solutions. Presenting a strong innovative character, COSMO-RS was evaluated for the description of the selectivities and capacities, showing to be a useful tool for the screening of ionic liquids in order to find suitable candidates for terpenes and terpenoids extraction, and separation. COSMO-RS predictions show that in order to achieve the maximum separation efficiency, polar anions should be used such as bis(2,4,4-trimethylpentyl)phosphinate or acetate, while high capacities require nonpolar cations such as phosphonium.

Keywords: Terpenes, Terpenoids, Ionic Liquids, Activity Coefficients at Infinite Dilution, COSMO-RS, Selectivity, Capacity.

2 ACS Paragon Plus Environment

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Introduction Essential oils are mixtures of volatile compounds isolated from animal and about 300 different plants species. Per year, 100,000 tons of volatile essential oils, with a value of about 1 billion US$, are produced worldwide for the food, flavour and fragrance industries. Apart from the volatile oils production, 250,000-300,000 tons of turpentine are also produced, from which about 100,000 tons are used for the production of terpenes and terpenoids.1 Terpenes and terpenoids have been used since the Egyptians civilization2 and their importance in both nature and human applications is enormous. The main reason for this great use is the abundance and diversity of these compounds in nature. Using a five carbon building block, the isoprene, nature creates an array of compounds with an wide range of structural variations and a vast number of applications.3 Structurally, terpenes are unsaturated hydrocarbons and they can also occur as oxygenated derivatives, called terpenoids.4 To be applied in food, perfumery, medicines and cosmetics, pure terpenes and terpenoids must be extracted from natural sources.2 Despite of their abundance, they are usually present in low concentrations, so they tend to be expensive or even uneconomic to exploit.3 However, when in high concentrations, terpenes and terpenoids mixtures can present undesirable properties, and then the deterpenation is imperative.5 For the production of pure compounds from natural materials, or for the deterpenation, the extraction of terpenes and terpenoids is of the utmost importance, being an area regarding eagerly for new technological developments. Vacuum and steam distillations, membrane processes, supercritical extraction, solvent (or liquid-liquid) extraction and chromatography are the techniques most used to remove hydrocarbons from essential oils.6 The solvent extraction is preferred, since this method requires less energy, than processes such as distillation and supercritical fluid extraction, while retaining the most volatile aliphatic chemicals7 and preserving the organoleptic properties of the original oil. To the best of our knowledge, the first study on terpene and terpenoids extraction dates back to 1959,8 and since then a vast number of works were published in this field.3 3 ACS Paragon Plus Environment


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Regarding the liquid-liquid extraction, water and several organic solvents have been investigated, as alcohols, acetonitrile, glycols and aminoethanol.6 Lately, another class of compound with exceptional properties have emerged as potential substituent for organic solvents, in the terpenes and terpenoids extraction, the ionic liquids (ILs).9–11 Ionic liquids are a neoteric class of compounds with adjustable characteristics as the miscibility and the polarity and exceptional properties as the non-volatility, chemical and thermal stability, large liquid temperature range and high solvating capacity.12 Many recent reviews summarize the large range of applications of ionic liquids in organic synthesis, catalysis, electrochemistry, and separation technology.13,14 To fully exploit the ILs potential in extraction and separation processes of terpenes and terpenoids and, in order to avoid a large number of experimental liquid-liquid extractions, screening methods to evaluate the best solvents are necessary. Solutesolvent interactions, selectivities and capacities can be derived from activity coefficients at infinite dilution ( γ 13∞ ).15,16 These can be determined from retention times using gas– liquid chromatography (GLC),17 and are related to the relative strength of intermolecular interaction of the solute with the ionic liquid. Prediction tools can also be used to the same end. COSMO-RS (COnductor-like Screening MOdel for Real Solvents) is a quantum chemical approach, proposed by Klamt and Eckert18 and used by several authors,19,20 for the a priori prediction of infinite dilution activity coefficients and other thermophysical data using only structural information of the molecules. This work reports on the application of infinite dilution activity coefficient data to select ionic liquids able to promote the separation and purification of terpenes and terpenoids. Thus, the γ 13∞ of 17 terpenes and terpenoids, in the ionic liquids composed by the cation 1-butyl-3-methylimidazolium, [C4mim]+, and the anions: chloride, Cl-; dimethyl phosphate, [(CH3)2PO4]-; methanesulfonate, [CH3SO3]-, and trifluoromethanesulfonate, [CF3SO3]-, are reported. The measurements were carried out using gas–liquid chromatography in the temperature range (398.15 to 448.15) K. The ionic liquids were chosen in order to evaluate the effect of the polarity of the anion and variations in their structure. The new data here gathered were used to evaluate the ability of COSMO-RS


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in the description of the selectivities and capacities for these compounds, and the model was then applied to screen different IL cations and anions for terpenes and terpenoids separation. Experimental Section The properties of the ionic liquids used in this work are presented in Table 1, while the terpenes and terpenoids description is available in Table 2 and Table S1. The procedure for ILs purification and characterization are given in Supporting Information. The water content was found to be below 300 ppm for all IL samples. Terpenes and terpenoids were used without any further purification. The infinite dilution activity coefficients were estimated from retention times measurements performed using a PerkinElmer Clarus 500 gas chromatograph through the GLC method detailed elsewhere.21,22 TURBOMOLE 6.1 program package was used to generate the COSMO-RS input files.23 The parameterization adopted was BP_TZVP_C30_1401 (COSMOconfX v3.0, COSMOlogic GmbH & Co KG. Leverkusen, Germany). The detailed experimental steps and the theoretical foundations for infinite dilution activity coefficients calculation are displayed in the Supporting Information, as well as the frameworks for molar excess thermodynamic functions or important separation quantities such as gas-liquid partition coefficients, selectivity or capacity. Results and Discussion Activity Coefficients at Infinite Dilution The experimental measurements of the activity coefficients at infinite dilution of terpenes and terpenoids in ILs were carried out between (398.15 and 448.15) K, with intervals of 10 K, and the average values at each temperature are presented in Table S2 of Supporting Information. High temperatures were adopted to avoid long retention times of solutes, and to prevent the solidification of the ionic liquids used inside the column. To better understand and explore the data, a comparison at a fixed temperature, 408.15 K, is presented in Figure 1. This temperature was chosen since it is the lowest temperature at which data are available for all the solutes studied in, at least, one ionic liquid.



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As shown in Figure 1, α-pinene and β-pinene show the weakest interactions with the ILs studied. This was expected since all the ionic liquids used present polar anions and thus, interact better with polar solutes as terpenoid alcohols, while the interactions with hydrocarbons (terpenes), and terpenoid ethers and ketones are weaker presenting higher values of activity coefficients at infinite dilution. The terpenoid linalool is a clear exception, presenting an increase in the activity coefficients at infinite dilution and, additionally, a change in the ILs trend, when compared with the other alcohols. Trying to rationalize this apparent outlier, the sigma profiles of all ILs and solutes in their most stable form were computed by COSMO-RS and are presented in Figure S1 of Supporting Information. The alcohols sigma profiles show that linalool is the only one that does not present an H-bond donor character. Since the ILs anions have an H-bond acceptor character, the interactions are weaker and, consequently, the γ 13∞ increase. Moreover, the change in the ILs trend suggests that in this case the anion-cation interaction is dominant face to the solute-anion interaction. Due to the long retention times, and to the TCD detector sensitivity limit, the activity coefficients at infinite dilution of a few alcohols, in some ionic liquids, were not possible to measure. However, in [C4mim][CF3SO3], the least polar IL,24 all solutes were measured. No significant differences were observed between the aromatic and the aliphatic terpenoids suggesting that the cyclical structure does not have a relevant impact in the activity coefficients at infinite dilution in the aromatic imidazolium ILs here investigated. In our previous work,25 measurements of γ 13∞ for organic solutes with the same ILs were carried out. Taking into account the functional groups, the same trend of γ 13∞ was found: hydrocarbons > ethers > ketones > alcohols. Moreover, the ILs trend observed for the infinite dilution activity coefficients magnitude was [CF3SO3]- < [(CH3)2PO4]- < [CH3SO3]- < Cl-, which is in good agreement with the polarity trend described by Cláudio et al..24 The dependency with the temperature is presented in Figure S2 of Supporting Information. For most solutes there is a linear increase or decrease in the natural logarithm of γ 13∞ with the reciprocal temperature. The compounds (–)-menthone, (S)6 ACS Paragon Plus Environment

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(+)-carvone and (1R)-(+)-camphor in [C4mim]Cl; (–)-menthone, geraniol and (1R)-(+)camphor

in

[C4mim][CH3SO3];

and

(1R)-(−)-fenchone

and

eucalyptol

in

[C4mim][(CH3)2PO4] and [C4mim][CF3SO3] present almost an independent behavior of the logarithm of γ 13∞ with the reciprocal temperature, and thus their enthalpy of solution is close to zero. Despite the large number of studies published on the measurement of infinite dilution activity coefficients of solvents in ionic liquids, to the best of our knowledge no data for infinite dilution activity coefficients of terpenes and terpenoids was previously reported using ILs as a stationary phase, and no comparison is possible. On an attempt to systematize the data collected here, correlations of the activity coefficients at infinite dilution of the terpenes and terpenoids measured with some of their properties (e.g. dipolar moment, solubility parameter, molar volume) were evaluated. The most promising results are reported on Figure 2 for the correlation with the solubility parameters calculated through the relation presented by Goharshadi and Hesabi.26 Results show a decrease of the activity coefficient at infinite dilution with the increase of the solubility parameter. Additionally, the different ILs presents almost parallel trend lines, suggesting a predictive character to be explored as soon as more data are available. Thermodynamic Functions at Infinite Dilution In order to obtain additional information concerning the interactions between the solutes and the ionic liquids, the partial excess molar properties at infinite dilution were analysed. The Gibbs energy, enthalpy, and entropy, for terpenes and terpenoids in the investigated ILs at T = 408.15 K, were calculated through the γ 13∞ values and are listed in table S3 of Supporting Information. As mentioned before, there are some solutes in some ILs that present a small variation with the temperature and hence, in those cases, the partial molar excess enthalpy at infinite dilution is close to zero. The partial molar excess properties as a function of γ 13∞ are presented in Figure 3. As can be seen, two different areas can be distinguished for ILs composed by the more polar anions (Cl−, [CH3SO3]−, [(CH3)2PO4]-), and three areas for the IL



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[C4mim][CF3SO3]. Region (I) and (II), common to all ILs studied, represents the E ,∞

ILs−organic solutes systems with positive deviations to Raoult’s law, γ 13∞ ( G m ) > 1. E ,∞

When H m

is also positive, region (I), no particular affinity between ILs and solutes

molecules is expected, as for hydrocarbons, ketones and ethers. Due to the weak interaction, these mixtures have potential to the formation of two immiscible phases. In region (II) both enthalpy and entropy are negative, clearly indicating the dominance of the entropic over the enthalpic effect. Indeed, in both regions, the partial excess enthalpy is close to zero, and the entropic effect is always dominant. [C4mim][CF3SO3] presents also region IV, with negative deviations from Raoult’s law (

γ 13∞ < 1). This region is characterized by favourable interactions between the solutes and the ILs, related with spontaneous dissolution, and consequently the enthalpic effect is dominant. The only solutes belonging to that region are carvacrol and thymol, both presenting strong polarity, where all the partial excess molar properties investigated are negative, showing that the HB between carvacrol and thymol, and the anion [CF3SO3]is favourable. The terpenoid linalool, highlighted before due to the absence of an Hbond donor region character, shows an extremely low value of the excess molar enthalpy at infinite dilution, when compared with all the other solutes. The interaction of this compound with the ILs is highly influenced by the temperature. Gas-Liquid Partition Coefficients

Gas–liquid partition coefficients, K L , were calculated from retention times using the densities of the pure ILs previously reported.25,27,28 Assuming an ideal gas phase, the gas-liquid partition coefficients can be used to understand the terpenes and terpenoids extraction using ILs, and their subsequently evaporation in order to recover the ILs, at low pressures. Moreover, these parameters are also useful to understand the role of ILs on the fractionation of a complex mixture of terpenes and terpenoids. Results at a fixed temperature are presented in Figure 4. In general, the highest values are observed for more polar solutes like alcohols, with the less polar IL, [C4mim][CF3SO3]. As expected, α- and β-pinene present the lowest values of the gas liquid partition coefficients, especially with the IL [C4mim]Cl. These coefficients indicate the possibility to separate


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terpenes from the terpenoid alcohol or ketone fractions. The K L always decreases with increasing temperature as can be seen in Table S4 of Supporting Information. Selectivities and Capacities

Selectivities, S ij∞ , and capacities, k ∞j , can be used to evaluate the ILs performance as solvents for separation processes.29–31 Taking into account the similarities in molecular structures and physical properties of terpenes and terpenoids, and therefore, the problems involved in their extraction from essential oils and subsequent fractionation, these two parameters must be known. According to the definition, a suitable solvent should present both a high selectivity and capacity for the components to be separated.32 Experimental results along with the selectivities and capacities predicted using COSMO-RS are schematically presented in Figure 5. The experimental capacity takes the highest values for the pairs containing thymol or carvacrol, when the anion of the IL is [CF3SO3]- (1.661 and 1.671, respectively), and the lowest values for the pairs containing β-pinene or eucalyptol in [C4mim]Cl (0.005 and 0.006, respectively). From the experimental selectivities it is possible to identify the most

complicated

separation

thymol/carvacrol, with a [C4mim][CF3SO3],

problems:

(-)-menthone/α-pinene

oxide

and

S ij∞ value close to 1 in the ILs [C4mim]Cl and

respectively.

Inversely,

the

pairs

linalool/thymol

and

linalool/carvacrol present high selectivity and capacity values with the IL [C4mim][CF3SO3], showing that this ionic liquid may be used in their separation. In general, experimental capacities are considerably lower than 1 and most of the selectivities fall in the range [1-2] and [2-4]. Selectivities ranges were chosen based on the numerical results obtained. Among the studied ILs, [C4mim][CF3SO3] is the one that seems to present high selectivities and capacities, indicating that ILs with low polarity should be used in the terpenes and terpenoids separation. However the major limitation that the ionic liquids studied in this work present are the low capacities that would prevent their application into a separation process. In order to improve the separation efficiency, new ILs must be evaluated. For that purpose an ILs screening, computed using COSMO-RS, was attempted. In order to validate COSMO-RS predictions, the ILs studied in this work were used. Figure 5 9 ACS Paragon Plus Environment


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shows that the selectivities obtained with COSMO-RS are generally lower than the experimental ones, which may be attributed to an over estimation of the hydrogen bonding interactions between ILs and solutes. Accordingly, COSMO-RS capacities are in general superior to the experimental ones. In spite of the quantitative deviations obtained with COSMO-RS from experimental data, in general the model is able to correctly estimate the order of the selectivities and capacities for the terpenes and terpenoids studied. A better agreement with the experimental data is obtained for the less polar ILs, such as [C4mim][(CH3)2PO4] and [C4mim][CF3SO3]. According with the experimental results obtained in this work, better selectivities and capacities are achieved with the less-polar ILs. As the COSMO-RS predictions seem to be more precise also for these compounds, a set of selectivities and capacities of terpenes and terpenoids with selected ILs was computed using COSMO-RS: cations, 1butyl-3-methyl-imidazolium, [C4mim]+; and trihexyltetradecylphosphonium, [P66614]+; were

combined

with

bis(trifluoromethylsulfonyl)imide,

the

anions

[NTf2]-;

tetracyanoborate,

[BCN4]-;

bis(2,4,4-trimethylpentyl)phosphinate,

[(C8H17)2PO2]-; tosylate, [TOS]-; methylsulfate, [CH3SO4]-; trifluoroacetate, [TFA]-; and acetate, [OAc]-. The ionic liquids were chosen based on the polarity of the cations and anions to cover a wide range of differentiated polarities between the ion pair. The most relevant cases unveiled by this search are presented in Figure 6, while the other compounds studied are presented in Figure S3 of Supporting Information. COSMO-RS predictions show that the higher selectivities are obtained using polar anions such as bis(2,4,4-trimethylpentyl)phosphinate or acetate; while to obtain high capacities nonpolar cations such as phosphonium based must be preferred. This indicates that terpenes and terpenoids extraction must be made using cations and anions presenting distinct characteristics in order to fulfill simultaneously the requirements of high selectivities and capacities. The experimental validation of these predictions and the use of these ionic liquids for terpene and terpenoids separation are currently under development in our laboratory. Among the compounds studied, a literature survey showed that an important separation problem is α-pinene/β-pinene, a mixture extracted from turpentine,3,33 usually by steamdistillation.34,35 The experimental results obtained for S ij∞ and k ∞j are presented in Table 3, along with selected COSMO-RS results and values from literature for some other 10 ACS Paragon Plus Environment

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important solvents. According to Table 3, it is possible to see that the experimental ILs studied present similar selectivities to the solvents studied by Díaz et al..36 However, the capacities are much lower. As discussed before, in order to increase the capacity, ionic liquids with low polarity must be used. [C4mim][CF3SO3] is the most promising solvent with respect to separation amongst the ILs experimentally evaluated in this work. Based on the COSMO-RS result for that IL, this is in agreement with the experimental information. Moreover, according to COSMO-RS the ILs [P66614][(C8H17)2PO2] and [P66614][OAc] show good potential to be applied as agent for the α-pinene/β-pinene separation Acknowledgements This work was developed in the scope of the projects CICECO-Aveiro Institute of Materials (Ref. FCT UID /CTM /50011/2013), financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement, and LSRE/LCM FCT UID/EQU/50020/2013). M.A.R.M thanks to FCT for the PhD grant SFRH/BD/87084/2012, to COST for the STSM Grant from COST action CM1206 and to Andrzej Marciniak and Michał Wlazło for the laboratorial support. B.S. acknowledges FCT for the award of the post-doctoral grant SFRH/BPD/38637/2007 and the award of the research project PTDC/AAC-AMB/121161/2010. Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Pure terpenes and terpenoids data, detailed experimental procedure and theoretical foundations, infinite dilution activity coefficients and partial molar excess enthalpies, gas–liquid partition coefficients, sigma profiles, activity coefficients at infinite dilution temperature dependence, and selectivities and capacities (PDF). Author Information Corresponding Author: Phone: +351 273303086; Fax: +351 273313051; E-mail: [email protected].



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Author Contributions: The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.


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(15) Letcher, T. M.; Marciniak, A.; Marciniak, M. Determination of Activity Coefficients at Infinite Dilution of Solutes in the Ionic Liquid 1-Butyl-3methylimidazolium Octyl Sulfate Using Gas−Liquid Chromatography at a Temperature of 298.15 K, 313.15 K, or 328.15 K. J. Chem. Eng. Data 2005, 50, 1294–1298. (16) Marciniak, A.; Wlazło, M. Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(2methoxyethyl)-1-methylpyrrolidinium trifluorotris(perfluoroethyl)phosphate. J. Chem. Thermodyn. 2013, 60, 114–119. (17) Domańska, U.; Marciniak, A. Activity Coefficients at Infinite Dilution Measurements for Organic Solutes and Water in the Ionic Liquid 1-Butyl-3methylimidazolium Trifluoromethanesulfonate. J. Phys. Chem. B 2008, 112, 11100– 11105. (18) Klamt, A.; Eckert, F. COSMO-RS: A Novel and Efficient Method for the A Priori Prediction of Thermophysical Data of Liquids. Fluid Phase Equilib. 2000, 172, 43–72. (19) Kurnia, K. A.; Pinho, S. P. S. P.; Coutinho, J. a P. J. A. P. Evaluation of the conductor-like screening model for real solvents for the prediction of the water activity coefficient at infinite dilution in ionic liquids. Ind. Eng. Chem. Res. 2014, 53, 12466– 12475. (20) Kurnia, K. A.; Pinho, S. P.; Coutinho, J. A. P. Designing ionic liquids for absorptive cooling. Green Chem. 2014, 16, 3741–3745. (21) Domańska, U.; Królikowska, M. Measurements of Activity Coefficients at Infinite Dilution in Solvent Mixtures with Thiocyanate-Based Ionic Liquids Using GLC Technique. J. Phys. Chem. B 2010, 114, 8460–8466. (22) Domańska, U.; Królikowski, M. Measurements of activity coefficients at infinite dilution for organic solutes and water in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate. J. Chem. Thermodyn. 2012, 54, 20–27. (23) University of Karlsruhe and Forschungszentrum Karlsruhe GmbH, TURBOMOLE V6.1 2009, 1989–2007, 25 GmbH, since 2007; available from http://www.turbomole.com. (24) Claudio, A. F. M.; Swift, L.; Hallett, J. P.; Welton, T.; Coutinho, J. A. P.; Freire, M. G. Extended scale for the hydrogen-bond basicity of ionic liquids. Phys. Chem. Chem. Phys. 2014, 16, 6593–6601. (25) Martins, M. A. R.; Coutinho, J. A. P.; Pinho, S. P.; Domańska, U. Measurements of activity coefficients at infinite dilution of organic solutes and water on polar imidazolium-based ionic liquids. J. Chem. Thermodyn. 2015, 91, 194–203. (26) Goharshadi, E. K.; Hesabi, M. Estimation of solubility parameter using equations of state. J. Mol. Liq. 2004, 113, 125–132. 14 ACS Paragon Plus Environment

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(27) Zech, O.; Stoppa, A.; Buchner, R.; Kunz, W. The Conductivity of ImidazoliumBased Ionic Liquids from (248 to 468) K. B. Variation of the Anion. J. Chem. Eng. Data 2010, 55, 1774–1778. (28) Gardas, R. L.; Freire, M. G.; Carvalho, P. J.; Marrucho, I. M.; Fonseca, I. M. A.; Ferreira, A. G. M.; Coutinho, J. A. P. High-Pressure Densities and Derived Thermodynamic Properties of Imidazolium-Based Ionic Liquids. J. Chem. Eng. Data 2006, 52, 80–88. (29) Wytze Meindersma, G.; Podt, A.; de Haan, A. B. Selection of ionic liquids for the extraction of aromatic hydrocarbons from aromatic/aliphatic mixtures. Fuel Process. Technol. 2005, 87, 59–70. (30) Jork, C.; Kristen, C.; Pieraccini, D.; Stark, A.; Chiappe, C.; Beste, Y. A.; Arlt, W. Tailor-made ionic liquids. J. Chem. Thermodyn. 2005, 37, 537–558. (31) Lei, Z.; Arlt, W.; Wasserscheid, P. Separation of 1-hexene and n-hexane with ionic liquids. Fluid Phase Equilib. 2006, 241, 290–299. (32) Lei, Z.; Dai, C.; Zhu, J.; Chen, B. Extractive distillation with ionic liquids: A review. AIChE J. 2014, 60, 3312–3329. (33) Schwab, W.; Fuchs, C.; Huang, F.-C. Transformation of terpenes into fine chemicals. Eur. J. Lipid Sci. Technol. 2013, 115, 3–8. (34) Langa, E.; Palavra, A. M. F.; Lourenço, M. J. V; Nieto de Castro, C. A.; Mainar, A. M. P, ρ, T and heat capacity measurements of (α-pinene + β-pinene) mixtures over the temperature range 283.15 K to 358.15 K and pressures up to 40 MPa: Experiments and modelling. J. Chem. Thermodyn. 2013, 57, 493–499. (35) Sama, J. K.; Bandopadhyay, P. Development of a simple method for separation of alpha-pinene and beta-pinene from turpentine oil and designing multicomponent batch distillation columns. Indian J. Chem. Technol. 2001, 8, 260–272. (36) Díaz, E.; Cortiñas, J.; Ordóñez, S.; Vega, A.; Coca, J. Selectivity of Several Liquid Phases for the Separation of Pine Terpenes by Gas Chromatography. Chromatographia 2004, 60, 573–578. (37) Domańska, U.; Bogel-Łukasik, E.; Bogel-Łukasik, R. 1-Octanol/Water Partition Coefficients of 1-Alkyl-3-methylimidazolium Chloride. Chem. Eur. J. 2003, 9, 3033– 3041. (38) Stark, A.; Zidell, A. W.; Russo, J. W.; Hoffmann, M. M. Composition Dependent Physicochemical Property Data for the Binary System Water and the Ionic Liquid 1-Butyl-3-methylimidazolium Methanesulfonate ([C4mim][MeSO3]). J. Chem. Eng. Data 2012, 57, 3330–3339. (39) Sheldon, R. Catalytic reactions in ionic liquids. Chem. Commun. 2001, 23, 2399–2407. 15 ACS Paragon Plus Environment


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(40) Yaws, Carl L., (2012; 2013; 2014). Yaws’ Critical Property Data for Chemical Engineers and Chemists. Knovel. Online version available at: http://app.knovel.com/hotlink/toc/id:kpYCPDCECD/yaws-critical-property/yawscritical-property.


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Tables Table 1. Name, structure, abbreviation, supplier, molar mass (M), melting point (TMP) and purity of the investigated ionic liquids. Chemical Formula Cation

Chemical Name

Purity

Supplier

M (g·mol-1)

TMP (K)

IoLiTec

174.67

341.9537

99

IoLiTec

234.32

≈ 353.1538

99

IoLiTec

264.26

< 253.15

98

IoLiTec

288.29

289.1539

99

Anion

(mass %)

1-butyl-3Cl

-

methylimidazolium chloride, [C4mim]Cl 1-butyl-3methylimidazolium methanesulfonate, [C4mim][CH3SO3] 1-butyl-3methylimidazolium dimethyl phosphate, [C4mim][(CH3)2PO4] 1-butyl-3-

F

O S

F F

O-

methylimidazolium trifluoromethanesulfonate,

O

[C4mim][CF3SO3]



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 30

Table 2. Names, structures, supplier, molar mass (M), boiling points (TBP) and mass fraction purities of the terpenes and terpenoids used. Chemicals

Supplier

CAS

M (g·mol-1) TBP (K)40

Mass fraction puritya

Terpenes α-pinene

SigmaAldrich

80-56-8

136.237

429.29

98%

β-pinene

SigmaAldrich

18172-67-3

136.237

439.19

99%

Terpenoids

(−)-borneol

Fluka

464-45-9

154.252

485.80

≥99%

(−)-Isopulegol

SAFC

89-79-2

154.252

480.98

≥98%

(−)-menthone

Fluka

14073-97-3

154.252

483.15

≥99%

Aldrich

7787-20-4

152.236

466.15

≥98%

(1R)-(+)-camphor

Aldrich

464-49-3

152.236

480.55

98%

(S)-(+)-carvone

Merck

2244-16-8

150.221

504.15

96%

Carvacrol

SAFC

499-75-2

150.221

510.15

99%

DL-citronellol

Sigma

106-22-9

156.268

496.40

≈95%

(1R)-(−)-fenchone

O


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Chemicals

M (g·mol-1) TBP (K)40

Mass fraction puritya

Supplier

CAS

Eucalyptol

Aldrich

470-82-6

154.252

449.55

99%

Eugenol

Aldrich

97-53-0

164.204

526.35

99%

Geraniol

SigmaAldrich

106-24-1

154.252

503.15

98%

L(−)-menthol

Acros

2216-51-5

156.268

487.40

99.7%

Linalool

Aldrich

78-70-6

154.252

470.15

97%

Thymol

Sigma

89-83-8

150.221

505.65

≥99.5%

α-pinene oxide

Aldrich

1686-14-2

152.236

489.51

97%

a

Declared by the supplier.

Table 3. Selectivities ( S ij∞ ) / capacities ( k ∞j ) at infinite dilution for α-pinene / β-pinene at 408.15 K in different solvents. Solvent [C4mim]Cl [C4mim][CH3SO3] [C4mim][(CH3)2PO4] [C4mim][CF3SO3] [C4mim][CF3SO3] – COSMO-RS [C4mim][(C8H17)2PO2] – COSMO-RS [P66614][(C8H17)2PO2] – COSMO-RS [C4mim][OAc] – COSMO-RS [P66614][OAc] – COSMO-RS Dinonyl phthalate Amine 220 Tricresyl phosphate Carbowax 6000 Ethylene glycol phthalate Carbowax 1500 a

Selectivities ( S ij∞ ) / capacities ( k ∞j ) 1.386 / 0.005 1.364 / 0.024 1.271 / 0.044 1.327 / 0.053 1.313 / 0.105 1.315 / 2.467 1.205 / 6.237 1.590 / 1.137 1.260 / 5.940 1.260 / 1.156 a 1.304 / 0.849 a 1.113 / 0.643 a 1.346 / 6.601 a 1.375 / 0.292 a 1.424 / 1.300 a

Reference

This work

36

Extrapolated value. 19 ACS Paragon Plus Environment


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Page 20 of 30

Figures

20

ACS Paragon Plus Environment

Page 21 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


Figure 1. Activity coefficients at infinite dilution of terpenes and terpenoids in the ILs studied, at 408.15 K. , [C4mim]Cl; , [C4mim][CH3SO3]; , [C4mim][(CH3)2PO4]; , [C4mim][CF3SO3].

21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Page 22 of 30

22


Page 23 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


Figure 2. Activity coefficients at infinite dilution as a function of the solubility parameters (calculated through 26) of terpenes and terpenoids in the ILs studied, at 408.15 K. Empty symbols were not used in the fit.

23



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Page 24 of 30


Page 25 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. Partial molar excess energies at infinite dilution as a function of the natural logarithm of the activity coefficients at infinite dilution of the terpenes and terpenoids in E ,∞

the ILs study, at 408.15 K. The full line represents G m E ,∞

, H m

and the symbols correspond to:

E ,∞

and ∆, Tref S m .



Figure 4. Experimental gas–liquid partition coefficients, K L , for terpenes and terpenoids in the ILs studied, at 408.15 K. , [C4mim]Cl; , [C4mim][CH3SO3]; , [C4mim][(CH3)2PO4]; , [C4mim][CF3SO3].

k ∞j

k ∞j

[C4mim]Cl - Experimental

β-pinene

[C4mim]Cl – COSMO-RS

Geraniol

DL-citronellol

L(-)-menthol

(-)-Isopulegol

(S)-(+)-carvone

(1R)-(+)-camphor

α-pinene oxide

(1R)-(−)-fenchone

Linalool

DL-citronellol (-)-menthone

(−)-borneol β-pinene

(−)-borneol Eucalyptol

Geraniol

Geraniol


Geraniol

L(-)-menthol

DL-citronellol

(−)-borneol

(S)-(+)-carvone

(-)-Isopulegol

L(-)-menthol

(1R)-(+)-camphor

L(-)-menthol

(S)-(+)-carvone

(S)-(+)-carvone

(1R)-(+)-camphor

(1R)-(−)-fenchone

(-)-Isopulegol

(-)-Isopulegol

(1R)-(+)-camphor

(1R)-(−)-fenchone

(1R)-(−)-fenchone

Linalool

Linalool (-)-menthone

(-)-menthone

(-)-menthone α-pinene oxide

α-pinene oxide

α-pinene oxide

β-pinene

Eucalyptol

Linalool

Eucalyptol

Eucalyptol

α-pinene

β-pinene

α-pinene

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 30

k ∞j

(-)-menthone

(1R)-(+)-camphor

(-)-Isopulegol

(S)-(+)-carvone

(1R)-(−)-fenchone

α-pinene oxide

(1R)-(+)-camphor

α-pinene

α-pinene oxide

(S)-(+)-carvone

(1R)-(+)-camphor

(1R)-(−)-fenchone

Eucalyptol

(-)-menthone

L(-)-menthol

k ∞j

[C4mim][(CH3)2PO4] - Experimental

β-pinene

[C4mim][(CH3)2PO4] – COSMO-RS

(1R)-(+)-camphor

(1R)-(−)-fenchone

(1R)-(+)-camphor

(1R)-(−)-fenchone

(S)-(+)-carvone

α-pinene oxide

(1R)-(+)-camphor

(S)-(+)-carvone (-)-menthone

(1R)-(−)-fenchone

(1R)-(+)-camphor Linalool

(1R)-(−)-fenchone

Eucalyptol

Linalool (-)-menthone

β-pinene

(-)-menthone α-pinene oxide

(-)-menthone

α-pinene oxide

Linalool

Eucalyptol

Linalool

α-pinene oxide

Eucalyptol

β-pinene

β-pinene

Eucalyptol

k ∞j

Linalool

(S)-(+)-carvone β-pinene

L(-)-menthol

(-)-Isopulegol α-pinene

L(-)-menthol

L(-)-menthol

(1R)-(−)-fenchone

(1R)-(+)-camphor

α-pinene oxide

(1R)-(−)-fenchone

Linalool

(-)-menthone

(-)-menthone

Eucalyptol

(-)-Isopulegol

β-pinene Eucalyptol

[C4mim][CH3SO3] – COSMO-RS

Linalool

β-pinene

α-pinene oxide

Linalool

β-pinene

[C4mim][CH3SO3] - Experimental

α-pinene

k ∞j

α-pinene

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Eucalyptol

Page 27 of 30



k ∞j

k ∞j

[C4mim][CF3SO3] - Experimental

[C4mim][CF3SO3] – COSMO-RS

Thymol

α-pinene

Thymol

Eugenol

(−)-borneol

(-)-Isopulegol

(1R)-(+)-camphor

(1R)-(−)-fenchone

Geraniol

(S)-(+)-carvone

L(-)-menthol

DL-citronellol

(-)-menthone

α-pinene oxide

β-pinene

Eucalyptol

Linalool

Carvacrol α-pinene

Thymol

Carvacrol

Eugenol

Eugenol

Thymol

L(-)-menthol

(S)-(+)-carvone

Eugenol

(S)-(+)-carvone

(−)-borneol

Thymol

(1R)-(+)-camphor

α-pinene oxide

Geraniol

(1R)-(+)-camphor

Geraniol

(−)-borneol

(-)-Isopulegol

(1R)-(+)-camphor

(1R)-(−)-fenchone

(1R)-(−)-fenchone

(S)-(+)-carvone (1R)-(−)-fenchone

(−)-borneol

DL-citronellol

(-)-Isopulegol

(-)-menthone

Geraniol

(1R)-(−)-fenchone

(-)-Isopulegol

(-)-menthone

L(-)-menthol DL-citronellol

DL-citronellol

L(-)-menthol

(-)-Isopulegol

Linalool

(-)-menthone

Linalool

α-pinene oxide

L(-)-menthol

Eucalyptol α-pinene oxide

α-pinene oxide

β-pinene Eucalyptol

β-pinene

β-pinene

Eucalyptol

α-pinene

Figure 5. Experimental and COSMO-RS predictions of S ij∞ and k ∞j of all solutes at 408.15 K in the different ionic liquids studied. Color code: [1-2]; [2-4]; [4-10]; [10-20]; [20-30]; and >30. Capacities, 5. k ∞j

Eucalyptol

(1R)-(−)-fenchone

Linalool

α-pinene oxide

Geraniol

(S)-(+)-carvone

(-)-Isopulegol

Thymol

(1R)-(−)-fenchone

L(-)-menthol

α-pinene oxide

Linalool

L(-)-menthol

DL-citronellol

Thymol

α-pinene oxide

(S)-(+)-carvone

(-)-Isopulegol

(1R)-(−)-fenchone

α-pinene

(1R)-(+)-camphor

Eugenol

Geraniol

(-)-menthone

Eugenol β-pinene

(-)-menthone Eucalyptol

L(-)-menthol

(−)-borneol

Thymol

Linalool

Eugenol

DL-citronellol

Linalool

DL-citronellol

Geraniol

α-pinene (-)-Isopulegol

Eucalyptol

α-pinene

α-pinene

β-pinene

(1R)-(+)-camphor

DL-citronellol

(−)-borneol

Geraniol

β-pinene

(S)-(+)-carvone

β-pinene

(−)-borneol

Eucalyptol

[P66614][NTf2] – COSMO-RS

(S)-(+)-carvone

Carvacrol

Carvacrol

(−)-borneol

Eugenol

[C4mim][NTf2] – COSMO-RS

(1R)-(+)-camphor

k ∞j

Carvacrol

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 30


Page 29 of 30

k ∞j

k ∞j

[C4mim][OAc] – COSMO-RS

[P66614][OAc] – COSMO-RS

DL-citronellol

(1R)-(+)-camphor

Eugenol

DL-citronellol

(1R)-(+)-camphor

α-pinene

(S)-(+)-carvone

Linalool

β-pinene

Thymol

L(-)-menthol

(1R)-(−)-fenchone

Geraniol

α-pinene oxide

Eucalyptol

(-)-menthone (-)-Isopulegol

Eugenol

(-)-menthone Carvacrol

Eugenol

Figure 6. S ij∞ and k ∞j of all solutes at 408.15 K in selected ILs, computed by COSMORS. Color code: Selectivities, [1-2]; [2-4]; [4-10]; [10-20]; [20-30]; and >30; Capacities, 5.


Eugenol

α-pinene DL-citronellol

(1R)-(+)-camphor

(S)-(+)-carvone (1R)-(+)-camphor

α-pinene

β-pinene (S)-(+)-carvone

DL-citronellol

β-pinene α-pinene

β-pinene

(1R)-(−)-fenchone

(S)-(+)-carvone

L(-)-menthol

Linalool

L(-)-menthol

L(-)-menthol

(1R)-(−)-fenchone

Linalool

Thymol

Thymol

Thymol

Linalool

(1R)-(−)-fenchone

Geraniol

Geraniol α-pinene oxide

α-pinene oxide

Geraniol α-pinene oxide

Eucalyptol

Eucalyptol (-)-Isopulegol

(-)-Isopulegol

Eucalyptol (-)-Isopulegol

Carvacrol

(−)-borneol

(−)-borneol

(−)-borneol

(−)-borneol

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Selection of Ionic Liquids to be used as Separation Agents for Terpenes and Terpenoids Mónia A. R. Martins1,2, Urszula Domańska2, Bernd Schröder1, João A. P. Coutinho1 and Simão P. Pinho3*

Table of Contents Graphic and Synopsis

Ionic liquids evaluation as solvents for extraction and entrainers in separation processes involving terpenes and terpenoids. 30 ACS Paragon Plus Environment

Selection of Ionic Liquids to be Used as Separation Agents for

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